In wireless communication networks, a common architecture is to provide a wireless base station device that serves as a gateway for wireless communications with each of multiple client devices, also called mobile stations. The base station may, for example, serve as a gateway to one or more wired networks. An example of such a network is one that involves wireless devices configured to comply with the communication protocol rules of the WiMAX™ communication technology.
A wireless client device transmits a so-called initial ranging signal to the base station in order to join the network for the first time. A ranging signal comprises a ranging code (e.g., a binary pseudo-noise code) of a predetermined number of bits (length) and there are a set of possible ranging codes allocated to a base station serving a coverage area or cell in wireless network. The base station responds to a received ranging signal with a ranging response that includes information such as transmission parameters (modulation type, coding rate and transmit power) and the wireless client device uses the received ranging response to determine timing offset in order to begin communicating data with the base station. This ranging mechanism may be repeated on occasion or periodically to update transmission parameters or to request bandwidth. In addition, a somewhat similar ranging process may be performed when a wireless client device is seeking hand-over from one base station to another base station.
Many modern wireless communication networks employ base stations that have multiple antennas and can therefore improve performance using beamforming techniques, both for received signals and transmitted signals. In most operating environments, a base station may be communicating with numerous wireless client stations. It is not uncommon for the base station to receive multiple ranging signals transmitted from wireless client devices at nearly the same time. Beamforming techniques can be exploited at the base station for the received signals, but due to the potential for overlap between ranging signals transmitted from two or more wireless client devices, traditional beamforming weight estimation techniques make it difficult to accurately estimate the receive beamforming weights to be used for a given ranging code in a received transmission.